Tsunamis are clearly on the radar now, in a way they never were prior to 2004, and are likely to stay there for many years. But just how big is the future threat? While the recent rash of lethal tsunamis is unusual, and this incidence unlikely to be maintained, tsunamis have always been with us and always be. The key question is: what can we do to counteract their destructive and lethal capacities?
The obvious place to start is by pinpointing those parts of the world where future tsunamis are most likely. Looking ahead, an imminent submarine quake off the south coast of Sumatra is certain to generate a major tsunami that will threaten the city of Padang; population 850,000. Elsewhere, earthquakes capable of triggering potentially devastating tsunamis can be expected sometime in the future in the Caribbean, off the coast of Chile and within the Manila Trench, close to the Philippines and Taiwan. Of greatest concern, going forward, is the Cascadia Fault, a 1200km long offshore structure stretching southwards from British Columbia in Canada to northern California, where the possibility of a magnitude 9 earthquake offers the prospect of the west coast of North America facing a tsunami on the scale of the Indian Ocean event.
Nature is the best defense
Knowing where a tsunami might happen is just the beginning. Measures then need to be put in place that will minimise injury and loss of life and, as much as possible, reduce the level of destruction. Computer modeling can provide some idea of the arrival height of a tsunami on a coastline and of how far it is likely to penetrate inland, although building such models is not straightforward and they are geographically specific. Physical barriers can be constructed to protect critical installations, such as nuclear power plants, but extending such protection for hundreds of kilometers along a vulnerable coastline is clearly not an option. Furthermore, make such barriers too low, as was the case for those around Japan’s Fukushima nuclear power plant, and they become essentially useless.
More effective is the preservation of coastal vegetation, such as mangrove forests, or the planting of coastal woodland, both of which have been shown to be effective in cushioning tsunami impact and breaking up the waves. Another straightforward but worthwhile means of limiting the impact of a tsunami on human lives and infrastructure involves ensuring that a strip of land immediately adjacent to the sea is kept free of homes and key public buildings, and used instead for recreational and other activities that do not require permanent facilities. The construction of escape roads capable of taking residents quickly inland and uphill can also make a valuable contribution towards saving lives.
Immediately following the events in the Indian Ocean, much of the attention on preventing such a catastrophe happening again focused on the development of tsunami warning systems. Such a system has been in place in the Pacific for more than 60 years and has proved to be a success in providing early warning of tsunamis, thereby saving lives. A comparable system has been operational in the Indian Ocean since 2006, and a number of countries, including Australia and Japan now have their own, although the effectiveness of the latter has to be questioned in light of the events of 2011. Such systems are not, however, very good at issuing alerts quickly enough to allow those communities who live close to the tsunami source to evacuate; the main reason why hundreds died in the Sumatran tsunami of 2010 despite the existence of the new Indian Ocean Tsunami Warning System. In circumstances where the first wave arrives within 15–30 minutes after the earthquake, time is of the essence. In the case of the Sumatran city of Padang, for example, it is estimated that even with advance warning, 95,000 people will remain within the inundation zone when the first wave strikes the shore.
Education, education, education
The only truly effective way of tackling this issue is through education; firstly making sure that vulnerable communities are familiar with the tsunami threat and secondly guaranteeing, through documentation, films, simulations and exercises, that people recognize the signs that a tsunami could be imminent and know how to respond quickly and effectively. The wholesale and rapid self-evacuation of communities immediately after an episode of severe seismic shaking or in response to the withdrawal of the sea, has the potential to slash the numbers of tsunami deaths in countries close to major submarine faults and in the smaller sea basins such as the Caribbean and Mediterranean, which tsunamis cross rapidly. While technology clearly has a key role to play in warning of tsunamis in transit, this concept, known as ESWAVE (Education for Self-Warning and Voluntary Evacuation) is now widely viewed as the means by which the impact of tsunamis on lives and livelihoods can be most effectively reduced.
As former British Prime Minister, Tony Blair, espoused in a different context, our best chance of ensuring that catastrophes such as those in the Indian Ocean and Japan never happen again is through “education, education, education.”